Conventional power semiconductor devices have been commonly used as a power supply device, and have been described in the following literatures.
1. Junichi Nishizawa: "High power-lateral junction FET of the character of a triode", Nikkei Electronics, 50.about.61, Sep. 27, 1971 PA0 2. J. Nishizawa, T. Terasaki, and J. Sibata: "Field-Effect Transistor versus Analog Transistor (Static Induction Transistor)", IEEE Trans. on Electron Device, ED-22(4), 185 (1975) PA0 3. J. Nishizawa and K. Nakamura: Physiquee Appliquee, T13, 725 (1978) PA0 4. J. Nishizawa and Y. Otsubo: Tech. Dig. 1980 IEDM, 658 (1980) PA0 5. Junichi Nishizawa, Tadahiro Omi, Moken Sha, and Kaoru Hontani: "Denshi-Tsushin Institute Technical Research Report", ED81-84 (1981) PA0 6. M. Ishidoh et al: "Advanced High Frequency GTO", Proc. ISPSD, 189 (1988) PA0 7. B. J. Baliga et al: "The Evolution of Power Technology", IEEE Trans. on Electron Device, ED-31, 157 (1984) PA0 8. M. Amato et al: "Comparison of Lateral and Vertical DMOS Specific On-resistance", IEDM Tech. Dig., 736 (1985) PA0 9. B. J. Galiga: "Modern Power Device", John Wiley Sons, 350 (1987) PA0 10. H. Mitlehner et al: Proc. ISPSD, 289 (1990): "A Novel 8 kV Light-Trigger Thyristor with Over Voltage Self Protection"
The above mentioned static induction semiconductor device has a device structure of a short-channel and a multi-channel in order to obtain low conduction loss, large current capability, high breakdown voltage, and high speed operation. In order to improve the high speed operation among these properties, it has been known to control a lifetime of carriers by diffusing Au, Pt and so on or by performing irradiation with electron beam or proton. In order to improve the large current capability, it has been also known to increase a surface area of a semiconductor device is suggested to obtain large current.
In the conventional static induction semiconductor device, if a part of a gate region is short-circuited to a cathode electrode, a channel region could not be pinched-off by a reverse-bias voltage because a gate current for turn-off is bypassed through the short-circuited region. That is, carriers existent in a N.sup.- region (including the channel region) at turn-off could not be swept out due to the short-circuit of the gate region to the cathode region. In other words, in the semiconductor device having a large surface area, an influence of resistance between the gate region and a point at which a lead wire for the gate region is drawn out cannot be neglected. Therefore, a large current could not be cut-off at a high speed due to a fact that a voltage drop is produced by a gate current of carriers flowing from the gate region to the drawn-out point of the lead wire of the gate electrode at turn-off and the turn-off operation might be effected by this voltage drop.
Moreover, when a high speed operation is attained by controlling lifetime of carriers, there is another problem that a conduction loss is increased due to a high on-resistance.
It is an object of this invention to solve the above problems of the conventional semiconductor devices and provide a semiconductor device, in which carriers remained within the gate region and N.sup.- base region can be swept out immediately at turn-off to increase a switching speed, while the low conduction loss, large current capability and high breakdown voltage can be maintained as there are.
It is another object of this invention to provide a semiconductor device, in which a switching speed can be increased and at the same time a conduction loss is decreased by reducing on-resistance.